We destory the roster in ev_disconnect_cleanup().
Adding a function to test if the roster has been destroyed and testing
for it in the statusbar.
So now when the connection is lost 'Lost connection' is printed in all
open windows.
We can then reconnect with `/connect accountname`.
Should fix https://github.com/profanity-im/profanity/issues/1083
Presence of contact not found in roster are filtered out.
But sometimes roster is received after a first few presences.
We choose to store presences until we receive roster and then process
this presences.
Fixes#1050
